The use of wind turbines for generation of electricity is becoming increasingly popular. A wind turbine typically comprises a rotor provided with rotor blades for transforming the wind to a rotary motion. The rotor is typically arranged for driving an electric generator. Since the wind typically rotates the wing at a relatively low speed and a modern generator is typically designed for operating at a relatively high speed, a gear unit is needed for stepping up the rotation speed of the turbine rotor to a speed suitable for an electric generator.
Wind turbines are often placed on high windturbine towers, which are erected in less densely populated areas or at sea. In order to facilitate installation and service, as well as to minimize the mechanical load on the wind turbine tower, a small volume and a low weight of the gearing is highly desirable. At the same time, the construction needs to be robust and tolerant to weather and load, since a remote wind turbine location may make the wind turbine difficult and time consuming for service personnel to access. Therefore, relatively light, simple, and reliable planetary gear units, which provide a high transmission ratio, are generally used.
US 2003/0123984 A1 discloses a wind turbine equipped with a planetary gear unit provided with helical planet gears. Each planet gear is journalled to a planet gear carrier in taper roller bearings, which are arranged in an “O” configuration for providing radial as well as axial support.
There is however a need for a gear unit offering higher reliability, lower weight, and/or lower cost of manufacture.